Unlicensed radio spectrum, often called the unlicensed band, has been allocated in various countries to allow devices or services to use spectrum without exclusion to other devices or services. For example, in the United States, the unlicensed bands at 2.4 GHz and 5 GHz do not require a license fee, and are available to be used by any device or service, within certain power and bandwidth limits. Similar conditions hold true for unlicensed bands in other countries. However, with freedom and zero cost spectrum comes overuse.
Market projections indicate that use of the unlicensed bands will grow significantly. As more devices use the unlicensed bands, the spectrum will become more crowded, which in turn will degrade the quality of service. Already, in the U.S., many experts have complained that the unlicensed bands have become a “garbage dump” due both to a lack of standardization and “greedy” use of spectrum by some devices, such as the 900 MHz band where many cordless phones were designed to operate. Thus, technology is needed to exploit the benefits of the unlicensed band without degrading the level of service that users expect.